1. Field of the Invention
The present invention relates to a method of simulating operating conditions of a telecommunication system including a plurality of radio base stations and a plurality of mobile transceivers.
2. Discussion of the Background
Such methods are currently used for optimizing, before actual physical implementation of a telecommunication system, a deployment of radio base stations forming a network in the system and a design of a decision-making network infrastructure to manage the network in order to define a telecommunication system that provides optimal communication service at the lowest possible cost.
Some simulation methods, known as mapping methods and currently used for optimizing GSM-type telecommunication systems, often referred to as 2G (second generation) systems, generate best-server maps showing geographical coverage areas, each area forming a cell including a single base station to assess the coverage of the system, following a general principle that if a mobile transceiver is located within a cell and if the associated base station is not saturated, the mobile transceiver will be provided with a satisfactory communication service.
An assessment of quality of service in UMTS-type telecommunication systems, often referred to as 3G (third generation) systems, cannot be accurately obtained by means of a method as described above, mainly because 3G systems do not perform a frequency planning as is done in 2G systems, where two different mobile transceivers located in a same geographical area are allocated two different communication frequencies to minimize interference between the mobile transceivers. In 3G systems, no such frequency planning is performed, so that communication interference between mobile transceivers can and will occur, which will adversely affect the quality of each ongoing communication to an extent which varies from one mobile transceiver to another according to the specific situation of each mobile transceiver, which extent cannot be predicted by means of the above-mentioned described methods.
Another known simulation method, usually referred to as Monte-Carlo method, mainly consists in generating a plurality of snapshots, each being descriptive of a predetermined, random-generated situation of the system. Each snapshot then shows the location of all mobile transceivers of the system in the corresponding situation, the base stations with which the mobile transceivers are communicating, and a level of power each mobile transceiver is applying to its ongoing communication, which enables to deduce the amount of interference the mobile transceiver generates for other mobile transceivers located in its vicinity, and thus the extent to which interference generated by other mobile transceivers adversely affects each single mobile transceiver in each random-generated situation. The operation of such a method is described, among others, in European Patent Application EP 1 148 658 A1.
The Monte-Carlo method hence enables to establish, for each random-generated situation, the number of mobile transceivers to which a satisfactory communication service is provided, and enables statistical assessment of the overall communication quality offered by the simulated system.
The amount of interference affecting each communication between a given mobile transceiver and an associated radio base station is represented by a value of an interference parameter, for example a signal-to-noise ratio, which is computed, in the known art, by means of complex formula which take into account all other communications simultaneously going on in the whole simulated telecommunication system, because of the lack of frequency planning in 3G systems.
Such formula can for example be expressed as follows:
For each mobile transceiver MSi, a signal-to-noise ratio SINRi,j representing the amount of interference affecting a communication involving the mobile transceiver MSi and generated by communications going on in a cell Cellj including a radio base station BSj is given by:
            SINR              i        ,        j              =                            P                      Ti            ,                          j              .                                      ⁢                  G                      i            ,            j                                                N          0                +                              ∑                          l              ≠              j                                ⁢                                    ∑                              k                ∉                                  Cell                  ⁢                                                                          ⁢                  j                                                      ⁢                                          P                                  Tk                  ,                                      j                    .                                                              ⁢                              G                                  i                  ,                  j                                                                    +                  α          ⁢                                          ⁢                      MS            ·            β            ·                                          ∑                                  k                  ∈                                      Cell                    ⁢                                                                                  ⁢                    j                                                              ⁢                                                P                                      Tk                    ,                                          j                      .                                                                      ⁢                                  G                                      i                    ,                    j                                                                                            ,
where PTij represents an amount of power transmitted by the radio base station BSj to the mobile transceiver MSi, Gij represents a coupling loss between the mobile transceiver MSi and the radio base station BSj., N0 represents a predetermined noise value, αMS represents an interference removal factor and β represents a channel orthogonality factor.
The overall signal-to-noise ratio SINRi representing the amount of interference affecting the communication involving the mobile transceiver MSi and generated by all communications going on in all other cells of the telecommunication system is then given by:
      SINR    i    =            ∑              All        ⁢                                  ⁢        j              ⁢                  SINR                  i          ,          j                    .      
It is easily understood that a computation of interference parameters such as the signal-to-noise ratios described above will require a huge amount of computing power, since the 3G telecommunication systems to be realistically simulated will typically involve thousands of radio base stations and hundred of thousands of mobile transceivers. Moreover, all values involved in such a computating step, like coupling loss values Gij and transmitted power values PTij, have to be stored in a memory and read during the execution of the computing step, which, again because of the enormous quantity of those values, will require huge memory space and processing power for performing all necessary read/write operations.
The present invention aims at ameliorating the above-mentioned problems, by providing a method of simulating operating conditions of a telecommunication system, which method requires less computing power and less memory space than currently used methods.